The present invention relates to pressure cookers of the types disclosed in U.S. Pat. Nos. 2,914,063, 3,314,416 and 3,976,218 in which the food is cooked in oil while maintained under pressure. The cooker is provided with a receptacle or vat in which the cooking oil is placed, the receptacle being covered by an hinged lid having a gasket around its perimeter which engages and seals against the upper edge of the receptacle when the lid is closed. In order to seal the lid against the receptacle, a locking mechanism is provided which includes a rigid lock bar having a latch at its front end which engages a tongue on the receptacle to latch the lid in place. The locking bar also mounts a spindle having a downwardly extending threaded rod which engages the lid, the arrangements being such that when the spindle is turned in one direction it exerts pressure on the lid and hence on the lid gasket and the top of the receptacle, thereby providing a pressure seal.
It is also been proposed to provide an interlock between the lid and the receptacle to prevent removal of the lid when the pressure within the receptacle is above a predetermined level. For example, as taught in U.S. Pat. No. 3,976,218, the lid is provided with a flexible metallic liner covering its inner surface, the liner serving in part as a diaphragm which engages a pin projecting through an opening in the lid. When the pressure within the receptacle exceeds a predetermined level, the flexible liner forces the pin outwardly for engagement with a locking collar forming a part of the spindle utilized to exert sealing pressure against the lid, the engagement of the pin with the locking collar preventing the spindle from turning in a lid-opening direction.
While the lid locking arrangements described above have been in widespread use, they are nonetheless subject to certain disadvantages. Paramount among these is the fact that unless the latch on the lock bar is securely engaged, there is the possibility that the latch will become disengaged and hence release the lid for opening movement irrespective of whether or not the spindle is locked. In addition, the closing and locking of the lid requires multiple manual operations, and also requires the use of both of the operator's hands.
In contrast to the foregoing, the present invention provides a simple and positive locking mechanism which permits one-hand operation.